Windows Sandbox is a new virtual machine environment coming to Windows 10 Pro and Enterprise versions in 2019, which will be available as an optional component within Windows. Microsoft details the upcoming feature in a blog post published yesterday, describing it as "a new lightweight desktop environment tailored for safely running applications in isolation".

"How many times have you downloaded an executable file, but were afraid to run it? Have you ever been in a situation which required a clean installation of Windows, but didn’t want to set up a virtual machine?

At Microsoft we regularly encounter these situations, so we developed Windows Sandbox: an isolated, temporary, desktop environment where you can run untrusted software without the fear of lasting impact to your PC. Any software installed in Windows Sandbox stays only in the sandbox and cannot affect your host. Once Windows Sandbox is closed, all the software with all its files and state are permanently deleted."

Microsoft lists these features for Windows Sandbox, outlining the secure and non-persistent "disposable" nature of the environment:

Part of Windows – everything required for this feature ships with Windows 10 Pro and Enterprise. No need to download a VHD!

Pristine – every time Windows Sandbox runs, it’s as clean as a brand-new installation of Windows

Disposable – nothing persists on the device; everything is discarded after you close the application

Secure – uses hardware-based virtualization for kernel isolation, which relies on the Microsoft’s hypervisor to run a separate kernel which isolates Windows Sandbox from the host

The environment requires a sytem with an AMD64 architecture running Windows 10 Pro or Enterprise build 18305 or later, with the rather slim minimum requirements of just 4GB of memory, 2 CPU cores, and 1 GB of free space (with 8GB RAM, 4 cores, and SSD storage recommended).

The full blog post goes into further detail with a full "under the hood" look at Windows Sandbox, which among other things offers graphics hardware acceleration "with Windows dynamically allocating graphics resources where they are needed across the host and guest".

As to availability, ZDNet's Mary Jo Foley had reported that while the feature was originally "expected to come to Windows 10 19H1 early next year" it could be available to Insider tester as early as this week with Build 18301 of Windows 10 - but this 18301 and earlier 18292 build referenced in Foley's post have apparently been removed from the Microsoft blog post, which now exclusively lists Build 18305.